US 7497013 B2
A dual base plate heatsink for use in dissipating heat for electronic devices with thermal contact between fins and the base plates and manufactured without welding. Separately extruded fins are connected to both base plates by placing the fins side by side in channels in both base plates. In order to couple the base plates and the fins, the base plates are maintained at a constant relative distance and a swaging tool is passed adjacent the fins and between the base plates in a direction parallel to the surface of the base plates. The swaging tool applies pressure to the base plates to thereby swage the base plates against the ends of the fins.
1. A method of manufacturing a dual base plate heatsink, said method comprising:
providing a plurality of heat-conducting fins, each of said fins with opposing ends;
providing two opposing heat conducting base plates, each of said base plates comprising an inward facing surface with a plurality of elongate landing areas thereon, each of said landing areas separated by an elongate channel;
inserting each of said ends of said fins into respective ones of said channels of each of said opposing base plates;
placing a first portion of a swaging tool between said opposing base plates, said swaging tool comprising a series of elongate tines, said series of tines dimensioned to be disposed adjacent each of said fins, each of said tines increasing in height from said first portion to a second portion;
while maintaining relative distance between said base plates, sliding said swaging tool adjacent said fins in a direction parallel to each said surface so that said second portion of each said tine increasingly applies pressure to a corresponding landing area, to increasingly swage each of said landing areas against each of said adjacent fins;
whereby swaging of each said landing area secures each said fin to each of said base plates.
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This invention relates in general to the manufacture of Heatsinks, and more specifically to a method for coupling fins in a high fin-density heatsink to dual heat-dissipating base plates.
Heatsinks are known in the art for receiving and then dissipating heat generated by electronic circuits in modern devices. Such well known heatsinks typically comprise one base unit to which the heat generating electronic devices are mounted, and a plurality of fins projecting from the base unit for dissipating the generated heat. It is a challenge to maximize the surface area of the fins in order to provide optimum heat transfer from the heat sink to the surrounding atmosphere while ensuring good thermal contact between the base unit and the fins.
Heatsinks fabricated by metal extrusion have been proposed, wherein the fins and the base units are of integral construction and thereby have the optimum thermal contact. However, as discussed in the disclosure of U.S. Pat. No. 5,406,698 (Lipinksi), it has been shown that there are limits to the size and shape of fins that may be made by way of extrusion manufacturing. There has thus been proposed various methods of manufacturing whereby the fins are extruded separately from the base unit, and subsequently coupled using various methods.
U.S. Pat. No. 5,771,966 (Jacoby) discloses a folded heat conducting member or fin with at least one annealed metal insert having a predetermined thickness corresponding to a distance between the first and second heat conductive portions of the fin and a predetermined thickness corresponding to a depth of the groove in the base plate so that the annealed metal insert conforms to the shape of the groove when deformed to secure the base portion engaging region of the folded heat conducting member into the groove. The Jacoby patent proposes an impacting die to perform a deforming or swaging function to deform the fin while in the groove so that it is not removable.
U.S. Pat. No. 6,263,956 to Tang et al. sets forth a heat dissipating structure and method of manufacture where each slot in the base has a width slightly less than a thickness of an inserting portion of the associated heat dissipating fin, so that it will allow the heat dissipating fin to tightly insert therein. A fixing frame is then moulded into place for securing the fins. The fixing frame is formed by introducing a melt fixing material inside of fixing recesses and thereafter cooling. As the material forms a solid, it forms the fixing frame that secures the heat dissipating fins onto the base.
Published U.S. Patent Application No. 2002/0007936 (Woerner et al.) discloses one or more folded-fin assemblies “tacked” to the base at selected points by laser welds. In a subsequent operation, the full surface of the lower web portions of the folded-fin assemblies are bonded to the base, typically by brazing. According to the Woerner disclosure, some suitable mechanical means is used to urge the lower web portions against the base prior to the laser welding, to optimize the contact between the lower web portions and the base when the subsequent brazing takes place. Also, a finger tool is used to maintain the desired spacing between adjacent fins prior to laser welding, to optimize that spacing and avoid the possibility of adjacent fins being positioned unevenly or in contact with each other. The heatsink assembly is said to be unloaded from the laser welding apparatus and taken for brazing, soldering or other suitable bonding to the base. As an example, the heatsink assembly may receive a spray application of flux which is then oven-dried and may be passed to a brazing furnace for heating to a temperature range of 1100-1120° F. to carry out the brazing.
Published U.S. Patent Application No. 2002/0043359 (Mizutani) sets forth a method of manufacturing a heatsink wherein fins are pressed by means of a mould so that protrusions provided on the back side of the metal plate are pressed into “bottom-expanded recesses” to fix the heat dissipation fins and the base plate together. Mizutani teaches an impact-die mold for pressing protrusions in the base plate against the fins to keep them secure to the base plate.
Mentioned above, U.S. Pat. No. 5,406,698 (Lipinksi), proposes a heat sink manufactured by providing a baseplate with several parallel grooves in its surface. Individual fins are manufactured having a dovetail or bell-bottom at their end, the ends then being inserted into respective grooves. The base plate is subsequently deformed in the areas between the parallel channels by rolling a plurality of coaxial rollers through the areas in order to crimp or swage the fins into the grooves. The Lipinski apparatus is an excellent design that requires little pressure to be transmitted though the fins themselves, so that their tendency to undesirably buckle under downward pressure is minimised. However, in the process of deforming the base unit in the areas between the parallel channels, the entire base unit tends to warp. To this end, U.S. Pat. No. 5,638,715 (Lipinski) sets forth an apparatus for subsequently reversing the warp effect.
With increased consumer demand for more complex electronic systems, the need has arisen for the more efficient use of space when manufacturing these systems. To help meet this demand, dual base plate heatsinks have been proposed that are mounted to more than one electronic device but that dissipate heat through a common set of fins. With these proposals have come a corresponding set of challenges for manufacturing the heatsinks to specifications that promote excellent heat transfer and good contact between the base plates and the fins. For example, the Lipinksi apparatus would not be sufficient for the manufacture of dual baseplate heatsinks because the proposed roller assembly would not be permitted to pass through the spaces between the fins once the second base plate was in place.
According to the present invention, a high fin-density dual base plate heatsink is manufactured by placing fins side by side in channels formed in each of two opposing base plates. In order to couple the base plates and the fins, the relative distance between the base plates is held constant and a swaging tool is passed both adjacent the fins and between the base plates in a direction parallel to the base plates. The pressure exerted by the swaging tool against the base plates adjacent the fins as the base plates are held at a constant relative distance swages the base plate adjacent each fin against the fin. Pressure is thus applied to the end of each fin inserted in each channel thereby securing the fin to the base plate.
A detailed description of the preferred embodiment is set forth in detail below, with reference to the following drawings, in which:
According to the present invention in its most general aspect, a dual base plate heatsink is manufactured by providing two opposing base plates, each with an inward facing surface and a number of elongate landing areas separated by elongate channels. Fins are placed into the channels of the opposing base plates and, while the base plates are being maintained at a constant relative distance, a swaging tool is passed in a direction parallel to the surface adjacent the fins and between the base plates. As the tool is passed it increasingly applies pressure to the landing areas of the base plate adjacent the fins to swage the base plate material against the fins. The swaging of the base plate causes pressure to be applied to the fins to force them to remain coupled to the base plates.
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Furthermore, the shape of each jaw 20 is shown clearly. The jaws 20 progressively widen in cross section from the end distal to the surface 14 of the base plate 12 towards the surface 14, and then narrow again. The base plates are maintained at a constant relative distance, as discussed in greater detail below with reference to
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A person understanding the present invention may conceive of alternatives and variations thereof. For instance, rather than employing slide-preventing walls for preventing the fins from sliding relative to the base plates, a pressure force can be applied to both base plates to increase the friction force between the fins and the base plates thereby reducing or prevent any relative movement. Furthermore, whereas the flared fin ends of the preferred embodiment provide a more uniform fit for better heat transfer with the jaw pairs when swaged, uniform thickness fins can also be used.
An alternative to the smooth-sided fin shape, whether flared or not, is to provide serrations on the end of the fin to improve bonding when the base plate material is deformed against the fin.
All such embodiments and variations are believed to be within the purpose, sphere and scope of the invention as defined by the claims appended hereto.